1. Field of the Invention
The present invention relates to a plasma processing apparatus that processes a semiconductor substrate using plasma, and more particularly, to the structures of a process vessel and a dielectric plate for the plasma processing apparatus.
2. Description of the Related Art
Recent years have seen a remarkable progress in semiconductor processing technology using plasma. Plasma processing has merits such that its process temperature can be far lower than conventional process temperature. A plasma processing apparatus generally includes: a process vessel housing a semiconductor substrate; an electromagnetic wave supply part supplying an electromagnetic wave to the process vessel; and a dielectric plate (dielectric window) disposed between the electromagnetic supply part and the process vessel. In an apparatus with such a configuration, mixed gas appropriate for the processing is introduced into the process vessel and plasma is excited by the electromagnetic wave such as a microwave. A sealing means such as an O-ring is interposed between the dielectric plate and the process vessel to vacuum-seals the process vessel.
In such a conventional plasma processing apparatus, however, due to a difference in thermal expansion coefficient between the dielectric plate and the metal process vessel, particles ascribable to friction, chipping, and the like of the metal vessel are produced in a contact portion of the dielectric plate and the metal process vessel. In the worst case, the dielectric plate suffers damage such as breakage. Further, local discharge occurs in an electric field boundary such as an edge portion of the dielectric plate, which not only gives damage to the metal vessel but also lowers efficiency of plasma processing such as film deposition of an oxide film.